Secondary battery

Abstract

A secondary battery includes: a case having an open end; an electrode assembly accommodated in the case; and a cap assembly coupled to the open end of the case and including a cap plate. A portion of the cap plate coupled to the case is thicker than other portions of the cap plate.

What is claimed is: 
     
         1 . A secondary battery comprising:
 a case having an open end;   an electrode assembly accommodated in the case; and   a cap assembly coupled to the open end of the case and comprising a cap plate, a portion of the cap plate coupled to the case being thicker than other portions of the cap plate.   
     
     
         2 . The secondary battery as claimed in  claim 1 , wherein the case has a rectangular parallelepiped shape, the cap plate has a rectangular plate shape, and a lower side of a long side portion of the cap plate is extended to form an extension portion. 
     
     
         3 . The secondary battery as claimed in  claim 2 , wherein the extension portion of the cap plate has a greater thickness than other portions of the cap plate. 
     
     
         4 . The secondary battery as claimed in  claim 3 , wherein a surface extending between the end of the extension portion and the lower surface of the cap plate has a streamlined cross-section. 
     
     
         5 . The secondary battery as claimed in  claim 3 , wherein a surface extending between the end of the extension portion and the lower surface of the cap plate has a straight cross-section. 
     
     
         6 . The secondary battery as claimed in  claim 3 , wherein a surface extending between the end of the extension portion and the lower surface of the cap plate has a stepped cross-section. 
     
     
         7 . A secondary battery comprising:
 a case having an open end;   an electrode assembly accommodated in the case; and   a cap assembly coupled to the open end of the case and comprising a cap plate, the cap plate having an extension portion at where lower portions of side surfaces of the cap plate, which face each other, extending toward the electrode assembly.   
     
     
         8 . The secondary battery as claimed in  claim 7 , wherein the case has a rectangular parallelepiped shape, the cap plate has a rectangular plate shape, and a lower side of a long side portion of the cap plate is extended to form the extension portion. 
     
     
         9 . The secondary battery as claimed in  claim 8 , wherein the extension portion of the cap plate has a greater thickness than other portions of the cap plate. 
     
     
         10 . The secondary battery as claimed in  claim 8 , wherein a surface extending between the end of the extension portion and the lower surface of the cap plate has a streamlined cross-section. 
     
     
         11 . The secondary battery as claimed in  claim 8 , wherein a surface extending between the end of the extension portion and the lower surface of the cap plate has a straight cross-section. 
     
     
         12 . The secondary battery as claimed in  claim 8 , wherein a surface extending between the end of the extension portion and the lower surface of the cap plate has a stepped cross-section.